Water cooled vacuum and pressure mold



Feb. 21, 1956 F. H. LUEHM ET AL 2,735,138

WATER COOLED VACUUM AND PRESSURE MOLD Filed March 30, 1953 5 Sheets-Sheet 1 F/mvc/s H. LUEHM fEUl V/NB. 5M1 TH INVENTORS Feb. 21. 1956 F. H. LUEHM E L WATER COOLED VACUUM AND PRESSURE MOLD Filed March 30, 1953 3 Sheets-Sheet 2 r 5 f P P zl"lilll7 all! 3.

INVEN TO L UEHM Femvc/s H, fED Y Feb. 21, 1956 LUEHM ETAL WATER COOLED VACUUM AND PRESSURE MOLD 3 Sheets-Sheet 3 Filed March 30, 1953 fNve-lvroeg Luz Hl'7 BY f B-ZM/TH W44 fl'r roausy.

Arcadia, Calii, to Arcadia, Caiiii, a corperatien mith, Cairesnt Carporaiion, of Caiif-ornia Application March 36, 1953, Serial No. 345,374 11 Claims. (-Cl. 18-26) This invention relates to a method and apparatus for the casting of tubular material from thermoplastic material.

it is an object of our invention to cast thermoplastic material to form thermoplastic tubes having accurately gaged inside and outside diameters with smooth walls.

It is another object of our invention to cast such tubular material to the exterior or interior surface of which sheet material, such as, for example, woven or knit fabric, may be adhesively secured.

These and other objects of our invention will be further described in connection with the drawings, in which Fig. l is a vertical plan view of the mold of our in vention with parts in section and parts broken away for clarity;

Fig. 2 is a section taken on the line 22 of Fig. 1;

Fig. 3 is a section taken on line 33 of Fig. 1;

Fig. 4 is a vertical section of one of the tubular molds;

Fig. 5 is a section taken on line 55 of Fig. 4;

Fig. 6 is a section taken on line 66 of Fig. 4;

Fig. 7 is a fragmentary detail of the mold;

Fig. 8 is a perspective view, partly in section, also showing the mold of our invention; and

Fig. 9 is a view with parts broken away of the cast tube removed from the mold.

The mold is formed of a plurality of tubular mold sections 1 composed of an outer tube 2 connected at the top to a tube sheet 3 by welds 4 which act as a closure for said tubes. The tubes at the bottom protrude through tube sheet 5 and are welded thereto at 6. The tube sheets are connected by jacket wall 8; thus the wall 8 and the tube sheets 3 and 5 form a chamber 9 through which the tubes pass. concentrically of each of'the tubes 2, the tube sheet 3 is bored to receive a pipe 9'. The pipes 9' are connected through valves 19 to a header 11 The jacket 8 is mounted for rotation on the stand 12 via hollow trunnions 13 and 14. Flexible inlet pipe 15 passes through the trunnion 13 through suitable stufiing box, as does flexible pipe 16 through trunnion 14. The pipe 15 is connected to inlet pipe 17 which reaches to near the top of the water chamber and the pipe 18 reaches to near the bottom of the water chamber and connects to the outlet pipe 16.

In using this mold to cast tubular objects lined with fabric liner or similar liner material, the mold is assembled as shown in Fig. 4,

The tubular mandrel 19, open at both ends, is slipped inside of a sleeve made of the material with which it is desired to line the interior of the tube of thermoplastic material. Such material may be either knit or woven stockinette material 29. The end of the stockinette material is tucked over the lower end of the tube 19. The top plate 23 has a circular flange 22 depending from the underneath side of the plate 23 and of exterior diameter so that it makes a clamping fit with the tube 19 so as to frictionally hold the fabric material at the top of the tube 20. The edges of the plate 23 are adjacent the interior surface of the tube 2 as will be described below. A plurality of bores 24 are placed in the plate 23 intermediate its periphery and the depending flange 22.

Into the bottom of the tube 19 is placed the bottom closure plate 25. The circular flange 26 is mounted on the upper face of the plate and is of outer diameter such that it makes a clamping fit with the tube 19 to hold the tucked in ends of the fabric. At the peripheral edge of the under side of the plate 25 is positioned a ring flange 27. Diametrically connected to this flange is the bar 28 which acts as a handle. Bayonet pins 29 are mounted at diametrically opposed points on the exterior surface of the ring 27. Adjacent the rings 27 a plurality of bores 30 are placed circumferentially of the plate 25.

Material similar to 20 and formed into tubular formation 31 and gathered at one end, as by a staple 32 to give a closed end, is slipped over the plates 23 and 25 to reach to the edge of the ring 27.

With the jacket 8 in horizontal position (see Fig. 8) this assembly is pushed into the tubes 2 and the bayonet pin 29 entered into the bayonet slot 33 formed in the end of the tubes 2 and the assembly is twisted to lock it in place. When in this position the end of the stockinette material makes a snug fit between the top surface of the plate 23 and the underneath side of the tube sheet 3, and between the inner surface of the tubes 2 and the circumferential edges of 23 and 25 and between ring 27 and the inner surface of 2.

The jacket is then up-ended to put it in a vertical position and a pot 34 full of molten thermoplastic material is raised and bolted to the horizontal flange 35 at the base of the jacket 8. A pipe connection 36 mounted in this flange makes a fluid connection with the pot to admit air under either atmospheric or super-atmospheric pressure over the top of the molten material in the pot. It will be observed that the ends of the tubes 2 are immersed in molten liquid to a depth to be described below.

Water is now admitted through pipe 15 and circulated upward through 17 through the jacket and pipe 13 and out pipe 16. The manifold 11 is connected to the vacuum pump 36 by opening the valve 37, valve 38 being closed (see Fig. 8). Valves 1b are then opened. Air is thus evacuated from tube 9', through the interstices of the fabric 31 and through the bores 24 through the annulus 2d and the holes 30 and over the fluid, thus drawing the fluid through the holes 30 into the annulus.

24' and over the fabric in the annulus. The vacuum is controlled to a degree shown on gage 40 to give the desired rate of fill into the annulus 24'. It will be understood that one or more than one of the valves lit may be opened as desired.

When the material has filled the annulus and reaches the bores 24 and enters these bores, the mass of the plastic inside these bores being small as compared to that in the annulus 24', the material congeals in con tact with the chilled plate 23. Vacuum suddenly rises as is evidenced by the gage. The entry of material thus automatically ceases since the air vent through 24 has been shut off.

It has been observed that if the vacuum maintained is excessively high, the material will enter at such rate as to be pulled through the bores 24 and into the pipe 9 before it is sufficiently chilled to close off the air communication to the vacuum pump. In such case, also, the cast tube shows striations and flow lines.

Experience has shown also that the mass of material in the annulus remains suflficiently fluid irrespective of the chilling at the surface of the tubes 2 to permit filling under flow conditions to give perfect tubular castings, and that all shrinkage during cooling is made up by the inflow of material from the pot, the depth of the liquid permitting this without uncovering the ends of the tubes 2;" After the vacuum use has indicated that the mold has been filled, Water is circulated to insure complete congelation and valves 37 and 19 are closed. The pot 34 is then removed and the mold rotated to horizontal position as shown in Fig. 8.

Air pressure is then established in manifold 11 by opening valve 38 in line connected to air compressor 41. In order to remove a tube, the-hinge 28 of the tube is grasped and the tube rotated to remove the pin 29 from the bayonet slot 33. At the same time the valve it is opened and air pressure against the plate 23, which thus acts'as a piston, pushes the cast tube carrying the mandrel 19 and the plates 23 and 25 out of the tube 2 (see Fig. 8).

There is thus presented (see Fig. 9) a cast tube 31 carrying a fabric liner 31 on its exterior surface and a liner 20 on the interior surface and mounted on the mandrel w to which the end plates 21 and are attached. A knife cuts the plastic material away at its juncture of the plates 23 and 25 to the cast material and the tubular mandrel is withdrawn from the lined plastic tube.

As will be understood by those skilled in the art, the above casting operation may be performed by omitting the sleeve 31 while retaining sleeve 24 or vice versa, by omitting the sleeve 20 while retaining the sleeve 31 and also by omitting both sleeves. In doing so, We may increase the dimensions of the tubes and plates to make a sliding fit to make up for the space occupied by the omitted fabric. However, one of the advantages of our process and apparatus is the ability to cast the tube and simultaneously line the outer or inner or both inner and outer surfaces of the cast plastic tube. The fabric also acts as a parting membrane to prevent adhesion of the cast material against the tubes 2 or the mandrel 19.

Experience has shown that when using the fabric as described above, the fabric surface adheres to the surface of the plastic and that the fabric interstices are not penetrated by the plastic material so that the plastic has a fabric surface uncoated by plastic.

We may employ any textile material stable at the casting temperatures, natural fibers such as cotton, flax, wool being useful when woven or knit into sheet or tubular material. Synthetic fibers, if used, must be chosen so that they will not be softened or their integrity destroyed or their utility impaired by the temperatures attained.

We may use any thermoplastic material which can be melted and cast. The thermoplastic synthetic resinous materials are now so well known that their itemization will serve no useful purpose. We have successfully employed the polyvinyl chloride and the polyvinyl chloride acetate copolymers described in the Lockwood Patent No. 2,525,177.

While we have described a particular embodiment of our invention for the purpose of illustration, it should be understood that various modifications and adaptations thereof may be made within the spirit of the invention as set forth in the appended claims.

We claim:

1. A mold, comprising an outer tube, a closure at one end of said tube, a valved port in said closure, a removable cylindrical mandrel in said tube, an exterior diameter of said mandrel being substantially less than the interior diameter of said outer tube, a plate at each end of said mandrel, one of said plates being positioned in said tube closely adjacent said closure, the other of said plates being positioned adjacent the opposite end of said tube, the edges of said plates being adjacent the inner surface of said tube, a plurality of ports in said plates between the edges of said plates and the exterior surface of said mandrel, said ports communicating with the annulus between the exterior surface of said mandrel and the interior surface of said tube, means for introducing molten material into the ends of said tube, and means for withdrawing air from said ports the ports in said one plate being sufficiently small to permit congealing of said molten material in said last named ports and to substantially prevent introduction of said material between said one plate and said closure.

2. A mold comprising an outer tube, a closure for one end of said tube, a port positioned axially of said tube, a removable plate positioned in said tube with one side of said plate closely adjacent the said closure, the edges of said plate being adjacent, but spaced from, the interior surface of said tube, a circular flange depending from the opposite side of said plate, an inner tube, said circular flange being positioned inside the inner tube, said inner tube being of smaller outer diameter than the inner diameter of said outer tube to form an annulus, a plurality of relatively small bores in said plate at said annulus, a second plate, a circular flange on one side of said second plate, said flange being positioned within the said inner tube, the edges of said plate being adjacent the inner surface of said outer tube, a plurality of bores in said plate at said annulus, means for introducing molten material through the said last-named bores into said annulus, and means for withdrawing air from said annulus through the bores in said first-mentioned plate and through said port.

. 3. A mold comprising an outer tube, a closure for one end of said tube, a port positioned axially of said tube, a removable plate positioned in said tube with one side of said plate closely adjacent, but spaced from, the said closure, the edges of said plate being adjacent, but spaced from, the interior surface of said tube, a circular flange depending from the opposite side of said plate, an inner tube, said circular flange being positioned inside the inner tube, said tube being of smaller outer diameter than the inner diameter of said outer tube to form an annulus, a plurality of bores in said plate at said annulus, a second plate, a circular flange on one side of said second plate, said flange being positioned within the said inner tube, the edges of said plate being adjacent, but spaced from, the inner surface of said outer tube, a ring flange at the periphery of said plate extending beyond the other side of said second plate, said periphery and the exterior surface of said last-named flange being adjacent, but spaced from, the interior surface of said outer tube, means on said ring flange for releasably locking same in position in said outer tube, a plurality of bores in said plate at said annulus, means for introducing molten material through the said last-named bores into said annulus, and means for withdrawing air from said annulus through the bores in said first-mentioned plate and through said port.

4. A mold comprising an outer tube, a closure for one end of said tube, a port axially positioned of said tube, a removable plate positioned in said tube with one side of said plate closely adjacent the said closure, the edges of said plate being adjacent, but spaced from, the interior surface of said tube, a circular flange depending from the opposite side of said plate, an inner tube, said circular flange being positioned inside the inner tube, said inner tube being of smaller outer diameter than the inner diameter of said outer tube to form an annulus, a water jacket about said outer tube, a plurality of relatively small bores in said plate at said annulus, a second plate, a circular flange on one side of said second plate, said flange being positioned within the said inner tube, the edges of said plate being adjacent the inner surface of said outer tube, a plurality of bores in said plate at said annulus, means for introducing molten material through the said last-named bores in said annulus, and means for withdrawing air from said annulus through the bores in said first-mentioned plate and through said portthe bores in said first named plate being sufliciently small to permit congealing of said molten materials in said last named bores and to substantially prevent introduction of said material between said plate and said closure.

5. A mold comprising an outer tube, a closure at one end of said tube, a valve port in said closure, a removable cylindrical mandrel in said tube, the exterior diameter of said mandrel being substantially less than the interior diameter of said outer tube, a plate at each end of said mandrel, one of said plates being positioned in said tube closely adjacent said closure, the other of said plates being positioned adjacent the opposite end of said tube, the edges of said plates being adjacent the inner surface of said tube, a plurality of ports in said plates between the edges of said plates and the exterior surface of said mandrel, said ports communicating with the annulus between the exterior surface of said mandrel and the interior surface of said tube, means for introducing molten material into the ends of said tube, means for withdrawing air from said ports, the ports in said one plate being sufliciently small to permit congealing of said molten material in said last named ports and to substantially prevent introduction of said material between said one plate and said closure means for releasably locking said mandrel and said plates in said outer tube, a compressor, a pipe connecting said compressor to said first named port, and a valve in said pipe.

6. A mold comprising an outer tube, a closure for one end of said tube, a port positioned axially of said tube, a removable plate positioned in said tube with one side of said plate closely adjacent, but spaced from, the said closure, the edges of said plate being adjacent, but spaced from, the interior surface of said tube, a circular flange depending from the opposite side of said plate, an inner tube, said circular flange being positioned inside the inner tube, said tube being of smaller outer diameter than the inner diameter of said outer tube to form an annulus, a plurality of relatively small bores in said plate at said annulus, a second plate, a circular flange on one side of said second plate, said flange being positioned within the said inner tube, the edges of said plate being adjacent, but spaced from, the inner surface of said outer tube, a ring flange at the periphery of said plate extending beyond the other side of said second plate, said periphery and the exterior surface of said last-named flange being adjacent, but spaced from, the interior surface of said outer tube, a plurality of bores in said plate at said annulus, means for introducing molten material through the said last-named bores into said annulus, means for Withdrawing air from said annulus through the bores in said first-mentioned plate and through said port, means on said ring flange and said outer tube for releasably locking said mandrel and said plates in said outer tube, a compressor, a pipe connecting said compressor to said port, and a valve in said pipe.

7. A mold comprising an outer tube, a closure for one end of said tube, a port positioned axially of said tube, a removable plate positioned in said tube with one side of said plate closely adjacent, but spaced from, the said closure, the edges of said plate being adjacent, but spaced from, the interior surface of said tube, a circular flange depending from the opposite side of said plate, an inner tube, said circular flange being positioned inside the inner tube, said inner tube being of smaller outer diameter than the inner diameter of said outer tube to form an annulus, a Water jacket about said exterior tube, a plurality of relatively small bores in said plate at said annulus, a second plate, a circular flange on one side of said second plate, said flange being positioned within the said inner tube, the edges of said plate being adjacent, but spaced from, the inner surface of said outer tube, a ring flange at the periphery of said plate extending from the other side of said second plate, said periphery and the exterior surface of said last-named ring flange being adjacent, but spaced from the interior surface of said outer tube, a plurality of bores in said plate at said annulus, means for introducing molten material through the said last-named bores into said annulus, means for withdrawing air from said annulus hrough the bores in said firstmentioned plate and through said port, the bores in said first named plate being sufficiently small to permit congealing of said molten matev ."al in said last named bores and to substantially prevent introduction of said material between said plate and said closure means on said ring flange and said outer tube for releasably locking said mandrel and said plates in said outer tube, a compressor, a pipe connecting said compressor to said port, and a valve in said pipe.

8. A mold, comprising an outer tube, a closure at one end of said tube, a valved port in said closure, a removable cylindrical mandrel in said tube, the exterior diameter of said mandrel being substantially less than the interior diameter of said outer tube, a plate at each end of said mandrel, one of said plates being positioned in said tube closely adjacent said closure, the other of said plates being positioned adjacent the opposite end of said tube, the edges of plates being adjacent the inner surface of said tube, a plurality of ports in said plates between the edges of said plates and the exterior surface of said mandrel, said ports communicating with the annulus between the exterior surface of said mandrel and the interior surface of said tube, means for introducing molten material into the ends of said tube, means for withdrawing air from said ports, the ports in said one plate being sufficiently small to permit congealing of said molten material in said last named ports and to substantially prevent introduction of said material between said one plate and said closure means for releasably locking said mandrel and said plates in said outer tube, a compressor, .a pipe connecting said compressor to said port, a valve in said pipe, a vacuum pump, a pipe connecting the vacuum pump to said port, and a valve in said last-named pipe.

9. A mold comprising an outer tube, a closure for one end of said tube, a port positioned axially of said tube, a removable plate positioned in said tube with one side of said plate closely adjacent, but spaced from, the said closure, the edges of said plate being adjacent, but spaced from, the interior surface of said tube, a circular flange depending from the opposite side of said plate, an inner tube, said circular flange being positioned inside the inner tube, said tube being of smaller outer diameter than the inner diameter of said outer tube to form an annulus, a plurality of bores in said plate at said annulus, a second plate, a circular flange on one side of said second plate, said flange being positioned within the said inner tube, the edges of said plate being adjacent, but spaced from, the inner surface of said outer tube, a ring flange at the periphery of said plate extending beyond the other side of said second plate, said periphery and the exterior surface of said last-named flange being adjacent, but spaced from, the interior surface of said outer tube, a plurality of bores in said plate at said annulus, means for introducing molten material through the said last-named bores into said annulus, means for withdrawing air from said annulus through the bores in said first-mentioned plate and through said port, means releasably locking said man-- drel and said plates in said outer tube, a compressor, a pipe connecting said compressor to said port, a valve in said pipe, a vacuum pump, a pipe connecting the vacuum pump to said port, and a valve in said last-named pipe.

10. A mold compri 'ng an outer tube, a closure for one end of said tube, a r t axially positioned of said tube, a removable plate pos oued in said tube with one side of said plate closely adjacent; the said closure, the edges of said plate being adjacent, but spaced from, the interior surface of said tube, a circular flange depending from the opposite side of said plate, an inner tube, said circular flange being positioned inside the inner tube, said inner tube being of smaller outer diameter than the inner diameter than the inner diameter of said outer tube to form an annulus, a water jacket about said exterior tube, a plurality of relatively small bores in said plate at said annulus, a second plate, circular flange on one side of said second plate, said flange being positioned within the saidinner tube, the edges of said plate being adjacent the inner surface of said outer tube, a plurality of bores in said plate at said annulus, means for introducing molten material through the said last-named bores into said annulus, means for withdrawing air from said annulus through the bores in said first-mentioned plate and through said port, means for releasably locking said mandrel and said plates in said outer tube, a compressor, a pipe connecting said compressor to said port, a valve in said pipe, a vacuum pump, a pipe connecting the vacuum pump to said port, and a valve in said last-named pipe.

11. A mold comprising an outer tube, a closure for one end of said tube, a port positioned axially of said tube, a removable plate positioned in said tube with one side of said plate closely adjacent, but spaced from, the said closure, the edges of said plate being adjacent, but spaced from the interior surface of said tube, a circular flange depending from the opposite side of said plate, an inner tube, said circular flange being positioned inside the inner tube, said inner tube being of smaller outer diamter than the inner diameter of said outer tube to form an annulus, a water jacket about said outer tube, a plurality of relatively small bores in said plate at said annulus, a second plate, a circular flange on one side of said second plate, said flange being positioned within the said inner tube, the edges of said plate being adjacent, but spaced from,

the inner surface of said outer tube, a ring flange at the periphery of said plate extending from the other side of said second plate, said periphery and the exterior surface ofsaid last-named ring flange being adjacent, but spaced from the interior surface of said outer tube, a plurality of bores in said plate at said annulus, means for introducing molten material through the said last-named bores into said annulus, means for withdrawing air from said annulus through the bores in said first-mentioned plate and through said port, the bores in said first named plate being sufficiently small to permit congealing of said molten material in said last named bores and to substantially prevent introduction of said material between said plate and said closure means for releasably locking said mandrel and said plates in said outer tube, a compressor, a pipe connecting said compressor to said port, a valve in said pipe, a vacuum pump, a pipe connecting the vacuum pump to said port, and a valve-in said last-named pipe.

References Cited in the file of this patent UNITED STATES PATENTS 29,416 Stanley July 31, 1860 342,420 Bingham May 25, 1886 753,959 Crump Mar. 8, 1904 2,396,406 Anderson Mar. 12, 1946 2,434,594 Schultz Jan. 13, 1948 

1. A MOLD, COMPRISING AN OUTER TUBE, A CLOSURE AT ONE END OF SAID TUBE, A VALVED PORT IN SAID CLOSURE, A REMOVABLE CYLINDRICAL MANDREL IN SAID TUBE, AN EXTERIOR DIAMETER OF SAID MANDREL BEING SUBSTANTIALLY LESS THAN THE INTERIOR DIAMETER OF SAID TUBE, A PLATE AT EACH END OF SAID MANDREL, ONE OF SAID PLATES BEING POSITIONED IN SAID TUBE CLOSELY ADJACENT SAID CLOSURE, THE OTHER OF SAID PLATES BEING POSITIONED ADJACENT THE OPPOSITE END OF SAID TUBE, THE EDGES OF SAID PLATES BEING ADJACENT THE INNER SURFACE OF SAID TUBE, A PLURALITY OF PORTS IN SAID PLATES BETWEEN THE EDGES OF SAID PLATES AND THE EXTERIOR SURFACE OF SAID MANDREL, SAID PORTS COMMUNICATING WITH THE ANNULUS BETWEEN THE EXTERIOR SURFACE OF SAID MANDREL AND THE INTERIOR SURFACE OF SAID TUBE, MEANS FOR INTRODUCING MOLTEN MATERIAL INTO THE ENDS OF SAID TUBE, AND MEANS FOR WITHDRAWING AIR FROM SAID PORTS THE PORTS IN SAID ONE PLATE BEING SUFFICIENTLY SMALL TO PERMIT CONGEALING OF SAID MOLTEN MATERIAL IN SAID LAST NAMED PORTS AND TO SUBSTANTIALLY PREVENT INTRODUCTION OF SAID MATERIAL BETWEEN SAID ONE PLATE AND SAID CLOSURE. 